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/**
* Copyright (C) 2019-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <map>
#include <string>
#include <boost/optional.hpp>
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/db/client.h"
#include "mongo/db/repl/repl_set_tag.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/string_map.h"
namespace mongo {
namespace repl {
/**
* Every Replica Set member has several views under which it can respond. The Split Horizon class
* represents the unification of all of those views. For example, a member might be reachable under
* "internal.example.com:27017" and "external.example.com:25000". The replica set needs to be able
* to respond, as a group, with the correct view, when hello requests come in. Each member of
* the replica set has its own `SplitHorizon` class to manage the mapping between server names and
* horizon names. `SplitHorizon` models a single member's view across all horizons, not views for
* all of the members.
*/
class SplitHorizon {
public:
static constexpr auto kDefaultHorizon = "__default"_sd;
using ForwardMapping = StringMap<HostAndPort>;
using ReverseHostOnlyMapping = std::map<std::string, std::string>;
using AllMappings =
std::tuple<SplitHorizon::ForwardMapping, SplitHorizon::ReverseHostOnlyMapping>;
struct Parameters {
boost::optional<std::string> sniName;
Parameters() = default;
explicit Parameters(boost::optional<std::string> initialSniName)
: sniName(std::move(initialSniName)) {}
};
/**
* Set the split horizon connection parameters, for use by future `hello/isMaster` commands.
*/
static void setParameters(Client* client, boost::optional<std::string> sniName);
/**
* Get the client's SplitHorizonParameters object.
*/
static Parameters getParameters(const Client*);
explicit SplitHorizon() = default;
explicit SplitHorizon(const HostAndPort& host, const boost::optional<BSONObj>& horizonsObject);
// This constructor is for testing and internal use only
explicit SplitHorizon(ForwardMapping forward);
/**
* Gets the horizon name for which the parameters (captured during the first `isMaster`)
* correspond.
*/
StringData determineHorizon(const Parameters& horizonParameters) const;
const HostAndPort& getHostAndPort(StringData horizon) const {
invariant(!_forwardMapping.empty());
invariant(!horizon.empty());
auto found = _forwardMapping.find(horizon);
if (found == _forwardMapping.end())
uasserted(ErrorCodes::NoSuchKey, str::stream() << "No horizon named " << horizon);
return found->second;
}
const auto& getForwardMappings() const {
return _forwardMapping;
}
const auto& getReverseHostMappings() const {
return _reverseHostMapping;
}
void toBSON(BSONObjBuilder& configBuilder) const;
private:
// Unified Constructor -- All other constructors delegate to this one.
explicit SplitHorizon(AllMappings mappings)
: _forwardMapping(std::move(std::get<0>(mappings))),
_reverseHostMapping(std::move(std::get<1>(mappings))) {}
// Maps each horizon name to a network address for this replica set member
ForwardMapping _forwardMapping;
// Maps each hostname which this replica set member has to a horizon name under which that
// address applies
ReverseHostOnlyMapping _reverseHostMapping;
};
} // namespace repl
} // namespace mongo
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